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Trees are the answer: to wastewater treatment for small communities: case studies

Trees are the answer: to wastewater treatment for small communities: case studies. By. J.G. Mexal, W. Zachritz, II, and T.W. Sammis New Mexico State University Las Cruces, NM. WF&CN Trees are the Answer….

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Trees are the answer: to wastewater treatment for small communities: case studies

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  1. Trees are the answer: to wastewater treatment for small communities: case studies By J.G. Mexal, W. Zachritz, II, and T.W. Sammis New Mexico State University Las Cruces, NM

  2. WF&CNTrees are the Answer…. • How can small communities dispose of wastewater in an economical and environmentally sound system? • How can poor communities generate income to maintain wastewater treatment systems? • Case studies: • Ojinaga, Mexico – Ismalia, Egypt • Las Cruces, NM – El Paso, TX • Valle de Juarez, Mexico

  3. WF&CNTrees are the Answer…. “Slow rate land application for wastewater treatment is a proven technology for municipal and other organic wastewaters. Used for over one-hundred years, it has evolved from a “disposal” method to one that can be used to recycle wastewater onto agricultural crops, forests, or park lands.” EPA 1992

  4. WF&CNTrees are the Answer…. • Mexico uses wastewaters without much consideration for quality or health concerns • California requires treatment that makes treated wastewater similar in quality to irrigation water • Both approaches are extreme resulting in excessive costs or potential health risks

  5. Facultative Lagoon Influent pipeline Effluent Sludge (solids) pipeline Biomass Plantation Trees are the Answer…. Idealized Schematic of Working System Municipal Untreated Sewage

  6. Trees are the Answer….Idealized Schematic of Working System H2O H2O H2O Applied Wastewater Soil/Air Interface 2 to 10 cm with active organic matter accumulation and aerobic microorganisms Active Rhizosphere 0.1 to 4 m with root growth and aerobic and anaerobic microorganisms Salt and Nutrient Accumulation Zone 4 to 120 meters with little microbial activity Subsurface and Groundwater Interface Leachate to Groundwater

  7. Trees are the Answer….Land Application Systems • In most land application systems, the land is an integral part of the treatment system, the waste is a source of nutrients, and the water is simply a carrier. • In arid environments, the water becomes a critical component of the system, especially if wastewater is the only source of water.

  8. Trees are the Answer….Land Application Performance

  9. Trees are the Answer….Wastewater Treatment Options

  10. Trees are the Answer….Wastewater Treatment Options

  11. Trees are the Answer….Land Application Systems- Major Considerations • Wastewater • Site • Soil • Crops • Climate • Markets • Management Goals • Treatment Needs

  12. Trees are the Answer….System Considerations • Wastewater Strength • Nitrogen • crop removal • 10 mg/L loading to groundwater • BOD5 • soil clogging • Salinity • crop sensitivity • leaching fraction

  13. Trees are the Answer….System Considerations • Soil Properties • slope • texture • depth to impervious layer or groundwater • rock content • Loading Rates • nitrogen • salt

  14. Trees are the Answer….System Considerations • Crop Characteristics • nitrogen removal • salinity tolerance • rooting depth • biomass production • Supplemental Irrigation • PET requirements

  15. Trees are the Answer….Community Backgrounds

  16. Trees are the Answer….Site Characteristics

  17. Ojinaga Case StudySite Characteristics • Population ~24,000 • Farming community;little industry • Flow 125 gpd (50% hookups) • Treatment = primary & discharge to river

  18. Ojinaga Case StudyRio Grande-Fecal Coliform Contamination IBWC 1997 Colonies / 100 ml 100 F M A M J J A S O N D J M 1997/ 1998

  19. Ojinaga Case StudyTree Performance / 3 yr Hybrid Poplar Eucalyptus

  20. Ojinaga Case StudyTree Performance / 4th yr survival Survival (%) E SC5 E4016 E4019 P 367 Robinia P 029 P 197 Time after Planting (mo)

  21. Ojinaga Case StudyTree Performance / Height Growth Height (m) P 367 E4019 E4016 E SC5 P 029 Robinia Time after Planting (mo)

  22. Ojinaga Case StudyTree Performance / -Diameter Growth DBH (cm) E4019 E4016 P SC5 P 367 P 197 P 029 Robinia Time after Planting (mo)

  23. Ojinaga Case StudyTree Performance / 4th yr Volume Stand volume (m3/ha) Green = vol. to 5 cm top White = total tree volume Species-clone

  24. Ojinaga Case StudyMonthly Water Requirement/1999 Actual PET/Ppt (in) Irrigation PET Ppt J F M A M J J A S O ND

  25. Ojinaga Case StudyGroundwater Quality 1 Contamination from monitoring well construction

  26. Ismailia, Egypt Case StudySite Characteristics • Located at southern end of Suez Canal • Secondary treatment of municipal wastewater • Cannot be used for crops destined for export; fruits, vegetables, cotton • Apply to tree crops (fuelwood, lumber, quality hardwoods, silk worm production)

  27. Ismailia, Egypt Case StudySite Characteristics Secondary treatment lagoon

  28. Ismailia Case StudyLand Application Site/June 2000 Italian cypress

  29. Ismailia Case StudyLand Application Site/June 2000 African mahogany 2 years old 5 years old

  30. Ismailia Case StudyLand Application Site/June 2000

  31. Ismailia Case StudyGroundwater Quality/April 2000

  32. El Paso, TX Case StudySite Characteristics • Blue jean washing and over-dyeing plant • Poor quality water • Dye operation requires salt mordant • Primary treatment and land apply to crop • current crop = alfalfa • interested in tree crop (ornamental or Christmas)

  33. El Paso, TX Case StudyWater Quality/TDS Concentration (mg/L) Well Influent 1o treatment W S S F Effluent Wastewater Parameter

  34. El Paso, TX ProjectSludge Application (Aug’00) Primary treatment lagoon Land application of sludge Dried cotton fibers & salts

  35. El Paso, TX ProjectSoil Chemistry after Irrigation Electrical Conductivity (mmhos/cm) 5 10 15 20 0 1 Soil Depth (ft) 2

  36. Las Cruces, NM Case StudySite Characteristics • West Mesa Industrial Park tenants • cheese processing (brine solution) • wire manufacturing (Cu, NaCl) • native plant nursery • human waste • Secondary treatment lagoons • Apply to native vegetation (mesquite, 4-wing saltbush)

  37. Case StudiesConclusion These case studies illustrate a sustainable, low cost, environmentally safe method of wastewater treatment is available to communities that can not financially support a conventional system. Furthermore, this approach can offer an economic return for communities lacking resources to construct traditional facilities.

  38. Case StudiesImplications for Nurseries • 1 MGD wastewater requires 100,000 to 200,000 trees for treatment (100-250 ac). • At least one nursery is offering consulting services for wastewater treatment using hybrid poplars. • Other nurseries could play an important role in economic development and wastewater treatment in communities.

  39. Ismailia Case StudyLand Application Site/June 2000

  40. Trees are the Answer….Design Equations Lw(n) = (Cp * (P - ET) + (U * 4.4)) ((1 - f)*Cn - Cp) where Lw(n) = allowable hydraulic loading rate (cm/yr); ET = design PET rate (cm/yr); P = design precipitation rate (cm/yr); Cp = total nitrogen in percolating water (mg/L); Cn = total nitrogen in applied wastewater (mg/L); U = crop nitrogen uptake rate (kg/ha/year); and f = fraction of applied total nitrogen removed by denitrification and volatilization

  41. El Paso, TX ProjectTDS (1992-2000) Well

  42. Ojinaga Case StudyMonthly Water Requirement/’Flat Rate’ PET/Ppt (in) Irrigation PET Ppt J F M A M J J A S O ND

  43. Ojinaga Case StudyTree Performance / 3 yr

  44. Ojinaga Case Study-Survival Survival (%) Time after Planting (mo)

  45. Ojinaga Case Study-Height Growth Height (m) Time after Planting (mo)

  46. Ojinaga Case Study-Diameter Growth DBH (cm) Time after Planting (mo)

  47. Case StudiesCritical Design Factors • Soil Infiltration and Site Slope • Wastewater Supply and Quality • Rainfall • Potential Evapotranspiration • Leachate Fraction for Salinity Control

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